Battery — concepts and standards

Designation: located on the battery case and specifies the characteristics of the battery. Example: «12V 40Ah 200A» (12V - rated voltage; 40Ah - nominal capacity; 200A - test current at low temperatures).

Rated voltage: total return (unit «IN»). All Focus models are 12V. The actual voltage depends on the state of charge of the battery. It can be more or less than the rated voltage.

Rated capacity: means the capacity of the battery, measured in amp-hours (Ag). This is the capacity that a fully charged battery can deliver for 20 hours at 27°C without dropping the voltage below 10.5V (discharged battery voltage). For example, the parking lights on your Focus use 25 watts. With an onboard voltage of 12 V, the battery according to the formula «current (A) = power (Tue), divided by voltage (IN)» delivers a current of 2.08A. With a 43Ah battery, theoretically, in about 20.3 hours, all the lights would go out in your Focus. We emphasize once again - theoretically, since in practice the battery is discharged after about 16 hours.

Capacity: delivered amount of current in ampere hours (Ah) It depends primarily on the discharge current, temperature, state of charge and the general condition of the battery (age).

Test current at low temperatures: means the starting capacity of the battery in cold weather (unit of measurement - ampere (A). A certain discharge current that can be taken from a battery with a voltage of 12 V at -18°C, while the voltage does not fall below 9 V for 30 s, below 6 V for 150 s.

Self-discharge: chemical processes in the cells of the battery lead to discharge, even if no consumer is connected. A charged new car battery loses about 0.5% of its charge daily. High temperatures, damage and contamination of the battery cover accelerate self-discharge.